1. Field of the Invention
The invention concerns a holder with clamps on its housing that move radially upon an axial movement of a pressure element, whereby the pressure element in located the housing can be acted axially upon by a first and second pressure medium, where the second pressure medium acts on the pressure element in the opposite direction as the first pressure medium.
2. Description of the Related Art
The document EP A 0255 042 (corresponding to U.S. Pat. No. 4,855,588), describes a holder in the form of a machine tool, e.g. a chuck attachable to an electrical discharge forming machine that can hold a work piece or tool. A tie bolt that couples with the workpiece fits in an opening of the chuck in which the tie bolt is held by a ball lock under the effect of pressure springs and can be released by compressed air acting against the pressure springs.
With the holder described in EP A 0614725 (correspond to U.S. Pat. No. 5,415,384), a pin projects from the workpiece to be held that can be held by a ball lock in a housing of the holder. The ball lock grips the pin under the effect of pressure springs acting on a pressure element. To release the workpiece, the pressure element is acted on by compressed air that acts against the pressure springs.